Process of dewatering sewage sludge and converting the same to a useable product

ABSTRACT

A PROCESS OF DEWATERING SEWAGE SLUDGE OR THE LIKE WASTE AND CONVERTING THE SAME TO A USEABLE PRODUCT WHEREBY THE SLUDGE IS PLACED IN A POROUS CONTAINER AND SATURATED WITH A WATER DISPLACING INGREDIENT SUCH AS TECHNICAL GRADE BUTANOL, AFTER A PERIOD OF TIME SUFFICIENT FOR DEHYDRATION TO OCCUR, THE CONTAINER PORES ARE CLOSED, AND TO THE SLUDGE IS ADDED A POLYMERIZABLE MATERIAL FOR A PERIOD OF TIME AT AN ELEVATED TEMPERATURE SUFFICIENT TO PERMIT COMPLETE POLYMERIZATION TO OCCUR.

. United States Patent Olhce 3,804,753 Patented Apr. 16, 1974 3,804,753PROCESS OF DEWATERING SEWAGE SLUDGE AND CONVERTING THE SAME TO A USEABLEPRODUCT Robert E. Baier, Buflalo, N.Y., assignor to Calspan Corporation,Bulfalo, N.Y.

No Drawing. Continuation of abandoned application Ser. No. 158,124, June29, 1971. This application Dec. 7, 1972, Ser. No. 313,071

Int. Cl. B01d 11/04 US. Cl. 210--21 8 Claims ABSTRACT OF THE DISCLOSUREA process of dewatering sewage sludge or the like waste and convertingthe same to a useable product whereby the sludge is placed in a porouscontainer and saturated with a water displacing ingredient such astechnical grade butanol, after a period of time sufiicient fordehydration to occur, the container pores are closed, and to the sludgeis added a polymerizable material for a period of time at an elevatedtemperature sufficient to permit complete polymerization to occur.

This is a continuation of application Ser. No. 158,124, filed June 29,1971 now abandoned.

BACKGROUND OF THE INVENTION The present invention is related to thetreatment of sewage sludge and, more particularly, the dewatering andconversion thereof to a useable product.

Municipal solid waste is dominated by hydrophilic biological entities,many having a fibrous nature. A black, malodorous, very wet mass calledactivated sludge is the intermediate byproduct of most current sewagetreatment plants; it is this byproduct that is the most difiicult andcostly to dispose of. There thus exists a need for a simple, moreeconomic scheme for dewatering and converting this activated sludge to auseable product.

Many techniques have been proposed for converting sewage sludge to auseable product, but in the main these have been costly, complicated andineffective.

For example a number of techniques require flocculation of the sludgewith a coagulant, scraping of the sludge onto large mesh screens forfurther dewatering and mechanical compression of the resulting product.Most of these techniques, as well as others, require the application ofenergy-consuming mechanical forces or processes.

SUMMARY OF THE INVENTION The present invention provides a process ofdisplacing the water from sewage sludge or hydrous waste of any originby a surface chemical mechanism without the requirement of energyconsuming mechanical forces. Additionally, the sludge product sodehydrated is in an extremely receptive state for infiltration withother organic materials including organic monomers and other solidprecursor type chemicals.

Basically the present invention contemplates placing the wet activatedsludge into a container corresponding in shape to the desired shape ofthe end product, the container having suit-able drain openings adjacentthe bottom thereof, distributing over the top of the sludge a waterdisplacing ingredient, such as technical grade butanol which percolatesthrough the sludge over a period of time, closing the drain openings ofthe container, and pouring over the sludge, still wet with the waterdisplacing ingredient, a suitable monomer and polymerization catalystwhich infiltrates the pores of the sludge, maintaining the sludge at anelevated temperature for a period of time sufiicient to permit completepolymerization to occur, after which the final product is removed fromthe container in the form of a dry, strong, sterile brick suitable foruse in construction or the like.

For a fuller understanding of the present invention, reference shouldnow be had to the following detailed description thereof.

DESCRIPTION Activated sewage sludge and other waste products consistprimarily of a fibrous mass of long chain polymeric molecules that arestrongly hydrophilic tending to form thixotropic gels of very high watercontent. It is this waste that, heretofore, has been the most difficultto convert or remove without adding to environmental pollution. Althoughthe foregoing description relates to sewage sludge, it is to beunderstood that any waste having the above characteristics can betreated.

According to the present invention the activated sludge is placed into acontainer, the shape of which is chosen to correspond to the shape ofthe final product. For example, a rectangular container would be chosenif a rectangular shaped brick is desired. The container is preferablyporous or has drain openings at the bottom thereof so that liquids arepermitted to escape. The sludge substantially fills the container. Asuitable water displacing ingredient such as technical grade butanol isslowly distributed over the top of the wet sludge and percolatedtherethrough over a period of time sufiicient to cause most of thedisplaced water of the sludge to drain through the porous bottom ofdrain openings of the container. The amount of water displacingingredient and time involved will depend upon the volume of sludge. Forexample with a container of 9 by 6 by 5 centimeters enclosing a volumeof 270 cubic centimeters and 90 cc. of butanol a time of about one hourwas sufficient. In addition to its water displacing function thistreatment also provides a first sterilization of the sludge.

With the dehydrated sludge still wet with the water displacingingredient, the bottom of the container is suitably covered to preventcontinued drainage of liquid. A suitable monomer and polymerizationcatalyst, such as tert-butylstyrene with benzoyl peroxide is poured overthe sludge in the container and the mixture is heated at a temperatureand a period of time sufficient for complete polymerization to occur. Inaddition to polymerization, this step functions as a secondsterilization step for the sludge. The temperature and time and amountof organic liquid will depend upon the volume of sludge being treated.For example, at a temperature of C., the above mentioned volume ofsludge took about 4 hours for complete polymerization. The amount oforganic liquid was 50 cc. of tert-butylstyrene with about 1% benzoylperoxide.

The resulting product is tapped out of the container in the form of adry, strong and sterile brick suitable for useful applications. 'In theabove example the brick was approximately 8.8 by 5.2 by 2.7 centimeters.

Although the foregoing description related to a preferred embodiment ofthe present invention, obvious changes will occur to those skilled inthe art. For example, instead of technical grade butanol as the waterdisplacing ingredient any aliphatic monohydric alcohol having from 4 to8 carbon atoms and a straight chain of at least 3 carbon atoms may beutilized. Additionally, instead of the tert-butylstyrene monomer anysuitable polymerizable material can be utilized so long as it is fluidenough that it can enter the pores of the dehydrated waste mass. Also,instead of the benzoyl peroxide polymerization catalyst, other knowntechniques or ingredients which initiate polymerization can be employed.For example, radiation can be used to initiate polymerization. Thiswould have an additional sterilization advantage.

It is therefore intended that the present invention is to be limitedonly by the scope of the appended claims.

What is claimed is:

1. A process of dewatering fibrous waste masses of long chain polymericmolecules such as activated sewage sludge and converting the same to auseable product comprising, the steps of:

(1) placing said waste into a container corresponding in shape to theshape of the desired end product,

(2) slowly distributing over the top of said waste a water displacingingredient which percolates therethrough over a period of timesuflicient to cause displaced water from said sludge to drain from saidcontainer,

(3) pouring a polymerizable fluid over said waste including apolymerization catalyst, and

(4) heating said waste for a period of time suificient for completepolymerization thereof to occur.

2. The process according to claim 1, wherein said container has drainopenings which are closed prior to the addition of said polymerizablefluid.

3. The process according to claim 2, wherein said water displacingingredient comprises an aliphatic monohydric alcohol having from 4 to 8carbon atoms and a straight chain of at least 3 carbon atoms.

4. The process according to claim 3, wherein said polymerizable fluidcomprises a monomer.

5. The process according to claim 4, wherein said monomer comprisestert-butylstyrene.

6. The process according to claim 5, wherein said tertbutylstyreneincludes a benzoyl peroxide polymerization catalyst.

7. The process according to claim 6, wherein said step of heatingcomprises heating said waste to a temperature of 80 C. for a period of 4hours.

8. The process according to claim 1, wherein said step of heatingcomprises heating said waste to a temperature of 80 C. for a period of 4hours.

References Cited UNITED STATES PATENTS 3,226,318 12/1965 Schick 210-103,365,395 1/1968 McDonald 210-66 X 3,527,698 9/1907 Von Reppert et al.2l010 3,436,342 4/1969 Fwiwara et al 21066 X JOHN ADEE, Primary ExaminerR. H. SPITZEE, Assistant Examiner U.S. Cl. X.R.

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